Microporous marking structures for use as marking structures on hand stamps may be made of suitable polymeric materials and resin (i.e., thermoplastic resin) or other open cell compositions which combine to form a slab-like structure including a large quantity of microscopic pores. The microporous structure may be impregnated with ink or other suitable marking fluid which fill many of the microscopic pores.
When such microporous marking structures are used as marking structures on hand stamps, they are commercially known as pre-inked hand stamps since they can be used to create thousands of impressions without applying additional ink to the marking structure. This is possible because the microscopic size of the pores allow the ink initially retained therein to escape at a controlled rate.
One brand of high quality pre-inked hand stamps are sold by M&R Marking Systems, Inc. of Piscataway, N.J. under the trademark ROYAL MARK. The pre-inked marking structures are made from ROYAL MARK brand gel which comprises a mixture of thermoplastic resin and ink. This mixture is also known as pre-mix used for manufacturing microporous marking structures.
Various methods of manufacturing such microporous marking structures exist. When microporous marking structures for use with currently available ROYAL MARK pre-inked hand stamps are manufactured, the ROYAL MARK pre-mix is poured into a mold. The mold is then heated in a vulcanizer at a predetermined pressure and temperature for a selected period of time. When this procedure is completed, the marking structure may be removed from the mold as a microporous slab. The manufacturing process is not yet completed at this time as the formed microporous slab retains too much ink to be placed on a hand stamp mount. It is therefore necessary to remove excess ink from the microporous marking structure prior to assembly on an associated mount. The process of removing such excess ink is known as stabilizing the microporous marking structure.
Another known method of manufacturing microporous marking structures contemplates initially forming a microporous structure which does not contain ink. The microporous structure is then impregnated with ink during a separate procedure. As with the aforementioned method of manufacturing microporous marking structures from a pre-mix which comprises thermoplastic resin and ink at the outset, the completed microporous marking structure includes excess ink which must be removed therefrom prior to assembly on an associated mount. Thus, stabilization procedures must be performed with all known methods of manufacturing microporous marking structures for use with pre-inked hand stamps.
Prior art inventors have exerted great effort to accomplish such stabilization. One well known commercially successful method has been employed by M&R Marking Systems. This method requires the placement of the microporous marking structure slab on newspaper, or other absorbent material in an oven where it is heated for a selected period of time. The heat causes the ink retained within the microscopic pores to flow out of the associated slab. This ink is then absorbed by the newspaper on which the marking structure is placed. The marking structure may then be removed from the oven and blotted with paper towel to absorb additional ink which has been caused to flow from the microscopic pores to the surface of the slab. The steps of heating and blotting the microporous slab to remove excess ink therefrom may be repeated several times.
When a desired amount of ink is removed from the microporous marking structure, it is considered to be stabilized and may be assembled on a mount.
Another known system for stabilizing microporous marking structures requires the use of negative pressure and a vacuum table. In accordance with the known negative pressure stabilizing system, a pre-inked microporous marking structure is placed on a vacuum table. Paper towel is then placed adjacent to the marking structure and a flexible plastic sheet is placed on top of the covered marking structure on the table. Vacuum suction is then applied through vacuum ports in the bottom of the table so that a negative pressure environment is created between the top surface of the table and the flexible plastic cover. Excess ink retained within the microscopic pores of the marking structure is extracted within the negative pressure vacuum environment and is absorbed into the paper towels. The negative pressure system does not include a controlled application of pressure and is largely dependent on user controlled parameters. Therefore, there is no control to assure that a consistently stabilized marking structure will be produced.
It is also known in the art to use cooperating rollers to remove excess ink from microporous stamp pads. This arrangement cannot practically be used to stabilize microporous marking structures intended for use with pre-inked hand stamps because it can lead to distortion of characters and does not provide sufficient control.
The present invention overcomes the shortcomings of the prior art by providing a method and apparatus for stabilizing microporous marking structures in a controlled environment wherein the required stabilization is accomplished in a short period of time and with more control than has heretofore been achieved.